java常用工具类，持续更新

import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StreamUtils;import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.Collections;
import java.util.List;/*** 描述：MyUtil 常用工具类* @see org.springframework.util.ResourceUtils* @see org.springframework.util.StreamUtils* @see org.springframework.util.CollectionUtils** @see org.apache.commons.io.IOUtils* @see org.apache.commons.io.FileUtils* @see java.nio.file.Files** @see org.apache.commons.collections4.ListUtils* @see org.apache.commons.collections4.CollectionUtils* @see org.apache.commons.lang3.StringUtils** @see javax.imageio.ImageIO* @see java.awt.image.BufferedImage*/
public class MyUtil {/*** 方法描述：<br/>* 从项目根目录【classpath】中读取文件并打印到控制台<br/>* 等价于{@link #readFileFromClasspath2(String)}* @param fileName* @throws IOException*/public static String readFileFromClasspath(String fileName) throws IOException {Resource resource = new ClassPathResource(fileName);try (InputStream inputStream = resource.getInputStream()) {return StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);}}/*** 方法描述：* 从项目根目录【classpath】中读取文件并打印到控制台* @param fileName* @throws IOException*/public static String readFileFromClasspath2(String fileName) throws IOException {File file = ResourceUtils.getFile("classpath:" + fileName);try (InputStream inputStream = Files.newInputStream(file.toPath())) {return StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);}}/*** 如果不是绝对路径的话，至少要【src/main/】开头* @param fileName* @return* @throws IOException*/public static String readFileFromFilesystem(String fileName) throws IOException {Resource resource = new FileSystemResource(fileName);try (InputStream inputStream = resource.getInputStream()) {return StreamUtils.copyToString(inputStream, StandardCharsets.UTF_8);}}/*** 获取项目所在位置* @return*/public static String getProjectLocation() {String userDir = System.getProperty("user.dir");return userDir;}/*** 获取项目所在位置* @return*/public static void printSystemProperties() {System.getProperties().forEach((k, v) -> System.out.println(String.format("%s=%s", k, v)));}/*** 打印当前执行代码所在的方法名称* @return*/public static String getCodeExecutePoint() {StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace();//第一个方法栈Thread.currentThread().getStackTrace()//第二个方法栈是封装的该方法：即：getCurrentClassLocation2()//第三个方法栈才是代码执行调用的方法StackTraceElement stackTraceElement = stackTraceElements[2];return stackTraceElement.toString();}/*** 方法描述：* 将异常信息转为字符串*/public static String getStackTrackFromException(Exception e) {try (StringWriter sw = new StringWriter(); PrintWriter pw = new PrintWriter(sw)){e.printStackTrace(pw);return "\r\n" + sw+ "\r\n";} catch (Exception var3) {return "getStackTrackFromException error";}}public static String defaultIfBlank(String str,String defaultStr){return (str==null||str.equals(""))?defaultStr:str;}public static String defaultIfNull(String str){return str==null?"":str;}public static List<?> defaultIfNull(List<?> list){return list==null? Collections.emptyList():list;}/***  使用ImageIO从网络上读取图片* @param inputUrl url 路径* @param outputPath 输出路径：可以时相对路径，也可是绝对路径*/public static void readImageFromUrl(String inputUrl,String outputPath) {// 图像 URL// String inputUrl = "https://example.com/input.jpg";// String outputPath = "output.png";try {// 从 URL 读取图像URL url = new URL(inputUrl);BufferedImage inputImage = ImageIO.read(url);// 对图像进行处理（这里只是简单地将其复制到另一个 BufferedImage 对象中）BufferedImage outputImage = new BufferedImage(inputImage.getWidth(), inputImage.getHeight(), BufferedImage.TYPE_INT_RGB);outputImage.createGraphics().drawImage(inputImage, 0, 0, null);// 写入图像ImageIO.write(outputImage, "png", new File(outputPath));System.out.println("写入成功！");} catch (IOException e) {e.printStackTrace();}}public static void main(String[] args) {try {readImageFromUrl("https://pics5.baidu.com/feed/b151f8198618367ae98737f813adabd9b21ce5f0.jpeg","output.png");// System.out.println(getCodeExecutePoint());} catch (Exception e) {e.printStackTrace();}}